Rules of the Day 3-28-07

Click here for today's lecture mechanism sheet

1. Tips for test preparation; what you need to know

Know the mechanisms, and understand how each step makes sense.

Know all the KRE's (Key Recognition Elements) for the different reactions, concentrating on the C-C bond-forming reactions

Know how to use the pKa table!

Know why pKa values are important for the Claisen mechanism

Be able to use all the reactions in the roadmap you have made

2. Tips for test preparation; what you should do to prepare

By yourself:

Master the reactions, mechanisms, KRE's, and analyze the homework and old exam answers. KNOW YOUR STUFF!

Make a sheet that lists the PRODUCTS of all the reactions first, then fill in the starting materials

With study partners:

Make up problems for each other in which you derive a product of a reaction. Show your study partner the products, and have them deduce the starting materials and reagents.

Make up synthesis problems for each other, by running a series of reactions on a randomly chosen starting material. Show your study partners the final product and the starting material, and have them fill in the rest.

3. There are four new concepts associated with chapter 19. Click on these one at a time to get more information.

A) Reactions favor the formation of weaker bases at equilibrium (provides a motive), so you need to have a Table of pKa values

B) Enolates as nucleophiles

C) Beta-Dicarbonyl species are especially acidic

D) Conjugate addition to alpha,beta unsaturated carbonyl species.

4. LDA is a wicked strong base that is not nucleophilic. It will quantitatively convert a carbonyl species into an enolate, so it can be used for crossed aldol or Claisen reactions.

5. The acetoacetate synthesis provides a simple way to make complex methyl ketones. The enolate is formed using 1.0 equivalent of strong base such as NaOEt, followed by 1) alkylation with an alkyl halide, 2) acid catalyzed hydrolysis of the ester and heating (loss of CO2). The initial acetoacetate can actually be alkylated twice if necessary.

6. A methyl ketone is the synthesis key recognition element (KRE) for synthesis by the acetoacetate synthesis.

7. The malonic ester synthesis is entirely analogous to the acetoacetate synthesis, except diethyl malonate is used and a substituted carboxylic acid derivative is the ultimate product following ester hydrolysis in acid (H3O+) and heating (loss of CO2).

8. A derivitized carboxylic acid function is the synthesis key recognition element (KRE) of the malonic ester synthesis. These can be tough to spot so practice.

Homework: Study for the midterm! Read: No new reading Problems: No new problems